Why is Beauty Smith's name unusual?

Smith's name is unusual because he is anything but a beauty.

No one knew his first name, and in general he was known in the country as Beauty Smith. But he was anything save a beauty. To antithesis was due his naming. He was pre-eminently unbeautiful. Nature had been niggardly with him. He was a small man to begin with; and upon his meagre frame was deposited an even more strikingly meagre head. Its apex might be likened to a point. In fact, in his boyhood, before he had been named Beauty by his fellows, he had been called “Pinhead.”